In the past spinal fixation systems have been implanted in open procedures involving relatively large incisions through the patient's tissue with significant muscle retraction. More recent procedures have been developed to introduce spinal fixation systems in a minimally invasive manner. One technique known as the Sextant® System is described in U.S. Pat. No. 6,530,929, issued to Justis, et al. In the '929 patent, separate incisions are made for introducing respective pedicle screws each attached to a tubular extension extending outwardly from the patient through each incision. A pivot arm coupled to the extensions introduces an elongate rod through another separate incision remote from the incisions receiving the extensions. The pivot arm urges the rod beneath the skin and into the pedicle screws for fixation. Other minimally invasive systems such as that shown in U.S. Pat. No. 7,306,603 issued to Boehm, Jr. et al. utilize tubular pedicle screw extensions to place a rod longitudinally through the extension into one of the pedicle screws. The rod is then pivoted about the pedicle screw through an incision between the pedicle screws to the second pedicle screw. Others still employ systems such as that shown in U.S. Pat. No. 7,250,052 issued to Landry et al. wherein slots in the screw extensions are used to guide a rod between the extensions through a single incision into position in two or more pedicle screws. Yet others provide spinal fixation systems as described in U.S. Pat. No. 8,142,437 (the '437 Patent), issued to McLean et al., and assigned to the same assignee as the subject invention. In the '437 patent, a rod introducer is provided for percutaneously inserting a connecting rod into slots of the screw extensions and into the yokes of the bone screws.
Yet despite advances in spinal fixation devices and techniques, there is still desire for implants, instruments and procedures for minimally invasively placing spinal fixation systems that are relatively simple and easy to use and that provide for enhanced assurance of rod introduction, connection to spinal implants and maintenance of rod position in the spinal fixation system.